JPH0115865B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to N,N-
The present invention relates to an electrophotographic recording material comprising a photoconductive layer forming at least one layer having a substituted 3,4,9,10-perylenetetracarboxylic acid bis-imide. In particular, the present invention relates to a recording material of a photoconductive layer forming a double layer that generates charge carriers and transports charge. A photoconductive layer of this arrangement is known, for example, from DE 2108992 (US Pat. No. 3,904,407). These documents describe a photoconductive layer consisting of a perylenetetracarboxylic acid bis-imide dye layer and a layer overlying said layer that carries charge and consists primarily of a polymeric photoconductor. The disadvantage of this arrangement is that the system has insufficient adhesion to the support and requires significantly longer drying times (2-24 hours) during production; this makes it difficult for industrial purposes. or suitability for industrial manufacturing is not guaranteed. DE 2237539 (U.S. Pat. No. 3,871,882) discloses that in order to obtain a photoconductor with sufficient adhesion and high sensitivity to light,
Photoconductor bilayers have been described which eliminate the aforementioned drawbacks by using monomeric organic photoconductors of sufficient conductivity and which can be treated with a number of binders. However, for specific industrial needs, even these photoconductor layers still have certain drawbacks: it is difficult to apply the charge-carrying layer to the vapor-deposited dye layer during the subsequent coating. . Furthermore, the deposition rate of continuous deposition of dye on the support is sufficient for low heat absorption in the case of red perylenetetracarboxylic acid bis-imide dyes, but is not at the optimal level, so that the formed dye The layer is not homogeneous under certain conditions and is disturbed by the formation of diffuse dark bands of dye aggregates (lumps) having a diameter of about 1 mm. Another significant drawback is that in the field of electrophotography, for example, when using He/Ne laser sources in the wavelength range ~630 nm, the good photoelectric sensitivity is relatively low in the case of perylenetetracarboxylic acid imide derivatives. or non-existence. It is therefore an object of the present invention to obtain an electrophotographic recording material which is superior to known materials in the range of its production conditions and the properties of its photoconductor, such as photoelectric sensitivity.
Taking the first-mentioned electrophotographic recording material as a starting point, this aim was to produce dark crystals of N,N'-bis-(3-methoxypropyl)-3,4,9,10-perylenetetracarboxylic imide. This is achieved if the modification is present as a dye that produces charge carriers. The crystalline form is identified by the extremely strong interference at 2θ = 6.2° in the X-ray diffraction diagram under Cu-Kα irradiation. The condensation product obtainable from perylene-3,4,9,10-tetracarboxylic anhydride and 3-methoxypropylamine provides a dye which overcomes the drawbacks and difficulties mentioned above, so that the charge carrier This dark colored dye is suitable for photoconductor purposes and is highly preferred.
The condensation products themselves are known from DE 24 51 781 as black dyes for polyethylene, polyvinyl chloride, surface coatings, inks and aqueous dye preparations. In continuous deposition in a vacuum evaporator, the dye according to the invention can be coated with other perylenetetracarboxylic acid derivatives,
For example, compared to N,N'-dimethyl-perylenetetracarboxylic acid imide, it can be used at significantly lower temperatures and under otherwise comparable conditions, such as vacuum, geometry, deposition rate and layer thickness. has advantages. At high deposition rates, the dyes according to the invention initially precipitate on the support with a substantial red hue. Investigation by X-ray diffraction shows that the material of the deposited layer is initially present in this metastable "red" crystal modified form, as shown by the X-ray diffraction diagram according to Figure 8b. It was done. Gradually at room temperature or during subsequent coatings, the crystalline form changes to a "dark" crystalline modification, as shown by the X-ray diffraction diagram according to FIG. 8a. During the coating process, it is very easy to disperse a dye layer initially deposited in a "red" color by converting its crystal structure, or to disperse a deposited dye layer that has already been converted into a dark crystalline form. It turned out to be a particular advantage. This results in a particularly good layer arrangement of adhesion, especially if the support is aluminum-coated polyester. Furthermore, using the dye according to the invention, as can be seen from curve K1 in FIG.
Spectral photoelectric sensitivity is approximately 80n for long wavelength range
spreads by m. By the way, for example, as shown by the curve K2 of N,N'-dimethylperylene-3,4,9,10-tetracarboxylic acid bis-imide in FIG.
Compared to the spectral photoelectric sensitivity of known perylenetetracarboxylic acid imide derivatives, it is possible to produce an electrophotographic recording material having a broadly uniform photoelectric sensitivity range of about 430 to 650 nm (FIG. 7, curve K1). Layers carrying a large amount of charge, for example electrophotographic recording materials, have been found to be optimal with respect to their spectral photosensitivity and their mechanical properties. Depending on the raw material preparation, the vapor deposition method, the dispersibility of the vapor-deposited dye layer and the single layer arrangement, such materials are very easily available. The combined advantages significantly improve the production of photoconductor layers, especially the arrangement of double layers, and result in electrophotographic recording materials with a wide range of uses. The invention will now be described with reference to the accompanying drawings. 1 is a conductive support, 2 is a dye layer that produces charge carriers, and 3 is a layer that carries charges. 4 is an insulating intermediate layer, and 5 is a layer constituting a dispersion of a dye layer that produces charge carriers. 6
is a photoconductive single layer consisting of a photoconductor, dye, binder, etc. The conductive support used is preferably an aluminum sheet or a transparent polyester film optionally vapor-deposited or laminated with aluminum, but any other support material rendered sufficiently conductive can also be used. . The photoconductor layer may be arranged on a drum, a flexible endless belt, for example a nickel or steel or other belt, or on a plate. The insertion of an insulating intermediate layer and optionally an aluminum oxide intermediate layer (FIG. 3, 4) produced thermally, anodically or chemically facilitates the injection of charge carriers from the metal into the photoconductor layer. The purpose is to reduce the On the other hand, it must prevent the flux of charge during the exposure process. The middle layer acts as a barrier layer. In some cases, the interlayer serves to improve the adhesion between the support surface and the dye layer or photoconductor layer. A variety of natural or synthetic resin binders can be used in the intermediate layer, but preferably one that adheres well to metal surfaces, especially aluminum surfaces, and undergoes little initial decomposition during subsequent use of other layers. Use materials that are no more than . These materials are polyamide resins, polyvinylphosphonic acids, polyurethanes, polyester resins or special alkali-soluble binders, such as styrene/maleic anhydride copolymers. The thickness of the organic interlayer may be up to 5 μm;
The thickness of aluminum oxide interlayer is generally 0.01~1μ
It is within the range of m. The dye layer 2 or 5, each consisting of or containing N,N'-bis-(3-methoxypropyl)-perylene-tetracarboxylic imide, has the function of a layer producing charge carriers; used in this case. In particular, the spectral photosensitivity of the multilayer photoconductive system is determined by the dye used and its absorption properties, which are shown in curve 1 of FIG. The use of a closely loaded homogeneous dye layer is preferably achieved by vapor deposition of the dye onto the support in vacuum. 1.33×10 ^-6 to 10 ^-6 bar without decomposing the dye by adjusting the vacuum and heating temperature
It can be deposited under conditions of 180-240°C. In that case the temperature of the support is below 50°C. In this way a layer with closely loaded dye molecules is obtained. Compared to all other methods,
This method results in a significantly thinner dye layer, which allows for an optimal generation rate of charge carriers in the dye layer, and the high absorption of the dye allows for a high concentration of excited dye molecules, allowing the dye layer to has the advantage that the transport of charge through the binder can only be hindered to a small extent or not at all by the binding agent. The preferred layer thickness range for vapor-deposited dyes is 0.005~
It is 3 μm. A thickness range of 0.05 to 1.5 μm is particularly preferred. This is because within this range the adhesion and uniformity of the vapor-deposited dyes are particularly good. By continuous deposition at a high rate of deposition in the vacuum of a deposition apparatus, the dye molecules initially form a "red" metastable modification, which upon gradual or heating at room temperature transforms into a dark crystalline modification. convert into things. During the next coating, a color change from red to blue-green takes place immediately. By contrast, during repeated deposition of dye in a rotating drum arrangement (corresponding to a low rate of deposition);
A stable blue-light green dye layer forms immediately. The perylenetetracarboxylic acid derivative according to the present invention is produced by dissolving perylene-3,4,9,10-tetracarboxylic anhydride and 3-methoxypropylamine in water in an autoclave at 130-140°C.
This can be achieved by carrying out a time condensation reaction. The dye is obtained in high yields of very dark brownish black crystals and is easily used after purification by dispersing in a slightly alkaline medium and washing free of alkali. Single color Cu
-Kα radiation (λ=0.154 nm) is used for the preparation of the X-ray diffraction diagram. Investigations have shown that N,N'-bis-(3-methoxypropyl)-perylenetetracarboxylic acid imide can exist in "red" or "dark" crystalline forms. Rapid discrimination between the two phases takes advantage of significantly stronger interferences at 2θ = 6.2° (Figure 8a, “dark” variant) and 2θ = 5.5° (Figure 8b, “red” variant). be able to. The dark crystalline form according to the invention is used for all other electrophotographic investigations. Besides dye vapor deposition, uniform dye thickness can also be obtained by other coating methods. These methods involve mechanically rubbing a finely divided dye material onto a conductive support, electrolytic methods or electrochemical methods using gun spray methods. In combination with or instead of an intermediate layer,
A homogeneous dye layer with sufficient application power and a thickness of 0.1 to 3 μm is prepared by applying the dye to a binder, in particular a highly viscous cellulose nitrate and/or an acrylic which may be crosslinked with a crosslinkable binder system, such as polyisocyanate. Grinding with a system consisting of an equal mixture of an acid resin, a reactive resin, such as an epoxide, or a crosslinked, hydroxyl-containing polyester or polyether, and a polyfunctional isocyanate, followed by a dye dispersion of these (Fig. 4). It can also be manufactured by coating the method shown in FIG. 5 and 5). The dye/binder proportions may then vary within wide limits, but pigment precoatings with a pigment proportion of greater than 50% and a correspondingly high optical density are preferred. It is also possible to produce photoconductor layers in which the charge carrier generating centers according to FIG. 1 are dispersed in the medium of the transport layer. Compared to double layers, this arrangement has the advantage of simple manufacturing. However, the disadvantage is that the dye particles are only excited on top of the photoconductor layer and therefore cannot exhibit their optimum effect. When p-carrying compounds are used, a photoconductor with a high photosensitivity when positively charged is produced by the inverted arrangement of the layer 5 which produces charge carriers on the charge-carrying layer 3 in FIG. A double layer is obtained. Suitable substances that serve to transport the charge are, inter alia, organic compounds with a wide π-electron system. These include monomeric and polymeric aromatic or heterocyclic compounds. The monomers used are especially those having at least one dialkylamino group or two alkoxy groups. Heterocyclic compounds described in German Patent No. 1058836 (US Pat. No. 3189447),
For example, oxadiazole derivatives have been found to be particularly suitable. These are especially 2,5-bis-
Contains (p-diethylaminophenyl)-1,3,4-oxadiazole. Other examples of suitable electron donor monomer compounds are triphenylamine derivatives,
Highly fused aromatic compounds, such as pyrene, benzo-fused heterocyclics, and also pyrazoline derivatives or imidazole derivatives (DE 1060714 and 1106599 corresponding to US Pat. No. 3,180,729 and UK Patent No. 938,434) Specification).
Furthermore, they are covered by German Patent No. 1060260, no.
1299296 and 1120875 (U.S. Patent No.
triazole derivatives, thiadiazole derivatives, especially oxazole derivatives, such as 2-phenyl-4-
Contains (2'-chlorophenyl)-5-(4'-diethylamino)-oxazole. Polymers that have been found to be suitable include formaldehyde condensation products with various aromatic substances, such as formaldehyde condensation products with 3-bromopyrene (DE 2137288, corresponding to US Pat. No. 3,842,038). Specification).
Furthermore, useful photosensitivity can be obtained with polyvinylcarbazole as carrier polymer, for example in a double layer arrangement. Without the dye layer, the charge-carrying layer is not photosensitive in the visible range (420-750 nm). Preferably this layer consists of a mixture of an electron donor compound and a resin binder if a negative charge has to be used. Preferably it is transparent, but this is not necessary in the case of transparent conductive supports. Layer 3 has a high electrical resistance of more than 10 ¹² Ω and prevents leakage of dark electrostatic charges. When exposed, this layer carries the charge generated in the organic dye layer. In addition to the aforementioned charge carrier-producing and charge-carrying substances, the added binder also has mechanical properties, such as abrasion, flexibility, film formation, etc., and also to some extent electrophotographic properties, such as photovoltaic properties. It has an effect on sensitivity, residual charge and cycling behavior. The binders used are film-forming compounds, such as polyester resins, polyvinyl chloride/polyacetic acid vinyl acetate copolymers, styrene/maleic anhydride copolymers, polycarbonates, silicone resins,
polyurethane, epoxide resin, acrylate,
Polyvinyl acetal, polystyrene, cellulose derivatives such as cellulose acetobutyrate and others. Furthermore, thermally crosslinking binder systems such as reactive resins consisting of equal mixtures of polyesters or polyethers having hydroxyl groups and polyfunctional isocyanates, acrylate resins which may be crosslinked with polyisocyanates, melamine resins , unsaturated polyester resins, and others have been used with good results. The use of cellulose nitrate, especially highly viscous cellulose nitrate, is preferred because of sufficient photosensitivity, flash sensitivity and high flexibility. The mixing ratio of charge-carrying compound and binder can be varied. However, suitably limited ranges are determined by the requirements for maximum photoelectric sensitivity, i.e. the proportion of the compound carrying the highest possible charge, and the requirements to avoid crystallization and increase the flexibility, i.e. the proportion of the binder as large as possible. I can be judged.
A mixing ratio of about 1:1 (parts by weight) has generally been found to be preferred, although ratios of 4:1 to 1:2 are also suitable. If charge-carrying polymeric compounds are used, such as bromopyrene resin or polyvinylcarbazole, binder proportions of about 30% or less are suitable. The special requirements of the reproduction device with regard to the electrophotographic properties and the mechanical properties of the recording material can be varied within wide limits by adjusting the layers in various ways, for example with regard to the viscosity of the binder or the proportion of charge-carrying compounds. exist. Besides the transparency of the charge-carrying layer, the thickness of the layer is an important factor for optimal photosensitivity: layer thicknesses of about 3 to 20 μm are generally used. Thickness range 4~
12 μm has been found to be particularly preferred. However, due to the mechanical requirements of the copying machine and the electrophotographic parameters (charging and developing locations),
The range may be greater or less than this on a case by case basis. Customary additives include leveling agents, such as silicone oils, wetting agents, especially nonionic substances, plasticizers of various compositions, such as those based on chlorinated hydrocarbons or on phthalate esters. do.
Optionally, conventional sensitizers and/or acceptors may be added as additives to the charge-carrying layer;
Only to such an extent that the optical clarity of the layer is not impaired. The invention will now be explained with reference to examples. Example 1 The dye N,N'-bis-(3-methoxypropyl)-perylene-3,4,9,10-tetracarboxylic acid imide (hereinafter referred to as perylimide) was deposited on a polyester film coated with aluminum under vacuum. 180 to 220 at 1.33 × 10 ^-7 to 10 ^-8 bar in vapor deposition equipment
℃ for 2 minutes; for comparison, N,
N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide is deposited at a temperature of about 280 DEG C. under otherwise identical conditions. A uniform vapor-deposited dye layer is
With a layer weight in the range 100-300 mg/m ² . The support is completely coated. When perylimide is deposited under these conditions, a dark-colored modification according to FIG. 8a is formed. However, if the rate of deposition is increased by depositing in a continuously operated vacuum deposition apparatus, a completely red-colored dye layer is formed, which gradually turns into a dark-colored modification. In the spectrophotometer reflectance curve (compared to aluminum-deposited polyester film), the spectral absorption of the dark perylimide layer (Fig. 6, curve K1) is approximately equal to the weight of the layer (110 mg/m ^{2 and 130 mg/m 2} ). m ² ) and a red dye layer (N,N′-dimethyl-perylene-3,4,
It is compared with the spectral absorption of 9,10-tetracarboxylic acid diimide, FIG. 6, curve K2). Example 2 Equal weight of 2,5-bis-(4'-diethylaminophenyl)-1,3,4-oxadiazole (melting point 149-150°C) (hereinafter referred to as oxadiazole)
and polyester resin in tetrahydrofuran (THF) is applied to the vapor-deposited perylimide dye layer from Example 1 on a rotating machine. The layer is then dried in a circulating air oven at about 110° C. for 5 minutes.
The layer thickness is 9-10 μm. The layers have good adhesion. The measurement of the photoelectric sensitivity is carried out as follows: In order to measure the light emission curve, the measurement specimen is moved to the exposure point on a rotating disk by means of a charging device and continuously moved with an XBO 150 xenon lamp (Osram). (Osram)]. A heat-absorbing glass and a 15% transparency neutral filter are placed in front of the lamp. The intensity of the light on the measurement surface is 50 to 100μW/
^cm2 ; measured using an optometer immediately after measuring the light attenuation curve. Charge levels and light attenuation curves are recorded oscillographically using an electrometer through a transparent tip. The photoconductor layer is characterized by the charge level (U _p ) and the time (T _1/2 ) at which half the charge (Uo/2) is obtained. T _1/2 and measured light intensity I
The product of &μW/cm ² § is the half-value energy E _1/2 &
μJ/cm ² §. The photoelectric sensitivity of the double layer is determined by this characterization method: (-) U _p (V) U _R (V, after 0.1 s) E1/2
(μJ/ ^cm2 ) 765 170
2.6 The residual charge (U _R ) after 0.1 seconds, measured from the above emission curve of light, is a measure of the discharge of the photoconductor layer. Comparison of a photoconductor bilayer consisting of a deposited layer according to Example 1, N,N'-dimethyl-perylene-3,4,9,10-tetracarboxylic acid diimide and a layer present on the former as described in this example. After preparation, the spectral photosensitivity is measured using a filter placed in front in the manner described above: for negative charge (800-850 V), half-life time (T _1/2 ) in milliseconds for a particular wavelength range.
determined by exposure. The spectral photoelectric sensitivity is obtained by measuring the mutual value of the product of the half-life time T _1/2 (seconds) and the light intensity I (μW/cm ² ) with respect to the wavelength λ (nm). The mutual value of T _1/2 xI (1/E _1/2 ) in this case represents the energy of light per unit area that must be radiated in order to discharge the layer to half the initial voltage U _p . The spectral photosensitivity of the bilayer with perylimide (curve K1) and N,N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide (curve K2) is described in FIG. Example 3 3-Brompyrene/according to German Published Patent No. 2137288 (U.S. Patent No. 3842038)
90 parts by weight of a formaldehyde condensation product and 10 parts by weight of a binder consisting of a copolymer of vinyl chloride and vinyl acetate are dissolved in THF and applied to the vapor-deposited perylimide layer to a thickness of about 7 μm (after drying). A further 90 parts by weight of poly-N-vinylcarbazole and 10 parts by weight of synthetic aliphatic and aromatic hydrocarbons of medium molecular weight are applied under the same conditions to a layer thickness of about 10 .mu.m onto the vapor-deposited perylimide layer. The photoelectric sensitivities of the two systems were measured according to Example 2, and the results are as follows:

[Table] Example 4 Perylimide was continuously applied to a polyester film coated with aluminum at 1.33% using a vacuum evaporator.
Deposition is carried out under ×10 ⁻⁷ bar at a temperature below 300° C. (measured at the surface of the dye) and at a speed of 30 m/min. The vapor-deposited dye layer is then successively coated with a solution of 65 parts by weight of oxadiazole and 35 parts by weight of standard type 4E cellulose nitrate [German Industrial Standard (DIN) 53179] in THF, and when dried, the color tone changes immediately. Changes from red to dark green. The weight of the layer is approximately 8 g/cm ² . A highly flexible and well-adhered photoconductor bilayer has the following photoelectric sensitivity (measured according to Example 2): charge: -620 V, half-energy: E _1/2 =
0.9: μJ/cm ² . Example 5 6 g of perylimide, 35 parts by weight of oxadiazole, 19 parts by weight of cellulose nitrate as in Example 4 and
It is dispersed in a solution of 270 parts by weight of THF, and the dispersion is vigorously milled in a ball mill at 3000 rpm for 2 hours. The finely dispersed dye dispersion is coated on a 100 μm aluminum foil with a thickness of 8 to 9 g/cm ² (after drying).
Apply with. By measuring the photoelectric sensitivity of this dispersion layer according to FIG. 1, the following values are obtained according to the measurement method described above. U _p (V) E _1/2 (μJ/cm ² ) (-)500 10.9 (+)600 15.5 Example 6 Equal parts of 2-phenyl-4-(2'-chlorophenyl)-5-(4'- diethylaminophenyl)-
A solution of oxazole (phenyl oxazole) and a copolymer of styrene and maleic anhydride as binder in THF was applied to a blue-green vapor-deposited perylimide dye layer according to Example 1, but with a layer weight of 370.
Apply with a rotating machine at mg/ ^m2 . 2-vinyl-4-
A photoconductor bilayer with (2'-chlorophenyl)-5-(4'-diethylaminophenyl)-oxazole (vinyloxazole) and the same binder in the transport layer is prepared in the same manner. The two solutions form excellent films with a thickness of 7-8 μm on the perylimide dye layer: Photosensitivity was measured as follows:

[Table] Example 7 A mixture of 84 parts by weight of perylimide dye and 14 parts by weight of acrylic resin which may be crosslinked with polyisocyanate in butyl acetate (concentration of about 10
%) is vigorously milled in a ball mill for 2 hours.
Before application, 2 parts by weight of a polyfunctional aliphatic isocyanate are stirred into the finely dispersed application batch, the mixture is diluted to approximately 5%, and a thickness corresponding to 360 mg/m ² is applied to aluminum foil (100 μm). Apply with. into the insoluble pigment precoat during the application of the transport layer,
When applying a solution of 65 parts by weight of oxadiazole and 35 parts by weight of cellulose nitrate according to Example 4,
A thickness of 7-8 μm is obtained. The photoelectric sensitivity (E _1/2 ) of this highly flexible and well-adhered photoconductor layer with the arrangement of FIG.
At 580V, E _1/2 = 5.7μJ/cm ² . Example 8 50 parts by weight of oxadiazole are combined with 50 parts by weight of various binders to form a vapor-deposited perylimide layer (200 mg/m ^{2 ).}
(thickness corresponding to
The good photoelectric sensitivities obtained by THF) are listed in the following table. It can be seen from the table values that the mechanical properties (flexibility, abrasion resistance, etc.) of the photoconductor layer are determined primarily by the nature and amount of the binder. With the arrangement according to the invention, well-adhering, highly sensitive photoconductor layers are obtained using many binders. This can be easily selected depending on the mechanical stress to be applied to the electrophotographic recording material during use.

Table Example 9 This example describes an inverted arrangement according to FIG. 5, which has a high photoelectric sensitivity in the case of positive charges. A solution of 60 parts by weight of oxadiazole and 40 parts by weight of cellulose nitrate according to Example 4 in THF,
Coat to a thickness of approximately 9 μm (after drying) on a 75 μm thick polyester film coated with aluminum.
Using a doctor blade, a finely divided perylimide dispersion with cellulose nitrate in a weight ratio of 1:1 is applied to this layer to a thickness of approximately 1 μm. After drying, by measuring the photoelectric sensitivity according to Example 2,
The following valence is obtained:

【table】 [Brief explanation of drawings]

1 to 5 are various longitudinal cross-sectional views of electrophotographic recording materials according to the present invention. FIG. 6 is a spectral absorption diagram of the dye layer. FIG. 7 is a spectral photoelectric sensitivity diagram. FIG. 8a is an X-ray diffraction diagram of the dark crystal modified product, and FIG. 8b is an X-ray diffraction diagram of the red crystal modified product. DESCRIPTION OF SYMBOLS 1... Conductive support, 2... Dye layer, 3... Charge carrying layer, 4... Insulating intermediate layer, 5... Dye layer, 6
...Photoconductive single layer.

Claims (1)

Claims: 1. An electrically conductive support, optionally an insulating interlayer and at least one layer comprising a perylenetetracarboxylic acid derivative as a dye producing a charge carrier and a photoconductor, a binder and customary additives. In electrophotographic recording materials consisting of a photoconductive layer, the dye present is a dark crystal modified product of N,N'-bis-(3-methoxypropyl)-perylenetetracarboxylic acid imide [this modified product has an X-ray diffraction line Figure (Cu−
An electrophotographic recording material that is identified by interference at 2θ = 6.2° with Kα irradiation.